1. Technical Field
The invention relates to a transporting apparatus that transports a transport target medium such as continuous-form paper used, for example, in printing, and a printing apparatus comprising the same.
2. Related Art
A printing apparatus 100 as one kind of a printing apparatus that performs printing on a transport target medium includes, as illustrated in FIG. 7, an imaging section 110 that continuously images the lower surface of the transport target medium transported by a transporting section (not illustrated), and a control section 140 that controls the operation of the transporting section and the imaging section 110 (for example, refer to JP-A-2014-87965).
The imaging section 110 includes a light emitting element 120 that applies light on the transport target medium, and an imaging element 130 that images the transport target medium based on the reflected light from the transport target medium when the light emitting element 120 applies the light on the transport target medium. As illustrated in FIG. 8, the imaging element 130 is an area image sensor in which a plurality of pixels is arranged in a two-dimensional manner in the horizontal direction and the vertical direction respectively in FIG. 8, and is divided into a valid pixel area 131 in which electric charge is accumulated in response to the reflected light introduced to the imaging element 130, and a shading area 132 that shades the reflected light.
As illustrated in FIG. 7, the control section 140 causes the light emitting element 120 to emit light by synchronizing to a vertical synchronizing signal output from the imaging section 110, computes transportation amount of the transport target medium based on the surface property of the transport target medium (image data) imaged by the imaging section 110, and controls the transporting section based on the computed transportation amount of the transport target medium.
The control section 140 performs a template matching process of moving the template of a rectangular area set in advance in the image on the transport target medium that was imaged at the previous time and on the image on the transport target medium imaged at the present time and searching the position in which the similarity is maximized in order to compute the transportation amount of the transport target medium.
That is, the control section 140 computes the distance in the transporting direction between the position of the template in the image that was imaged at the previous time and the position of the template matched in the image imaged at the present time as the transportation amount.
Meanwhile, the vertical synchronizing signal output from the imaging section 110 is a signal synchronized to the timing of transmitting the image data of the transport target medium imaged by the imaging section 110 to the control section 140. In addition, the timing of the imaging section 110 transmitting the image data of the transport target medium to the control section 140 changes due to the specification of the imaging section 110. Because of this, the timing of the imaging section 110 outputting the vertical synchronizing signal to the control section 140 changes due to the specification of the imaging section 110, and the timing of emitting light of the light emitting element synchronized to such a vertical synchronizing signal also changes due to the specification of the imaging section 110. As a result, in the timing of emitting light of the light emitting element, there is a concern that a streak is generated in the image data, and a concern that the light emitting element 120 emits light at the duration of reading of the valid pixel area 131 of the imaging element 130.
For example, in the case where the light emitting element 120 emits light when a part of a dashed line of the valid pixel area 131 in FIG. 8 is read, the image data of the valid pixel area 131 changes with the dashed line as a boundary as in the following. In other words, in an area 131A which is an area at one side of the vertical direction from the dashed line in the valid pixel area 131, and in which pixels are already read, the image data when the light emitting element 120 emitted light at the previous time is the image data of the area 131A. In addition, in an area 131B which is an area at the other side of the vertical direction from the dashed line in the valid pixel area 131, and in which pixels are not read yet, the image data when the light emitting element 120 emits light at the present time is the image data of the area 131B. In other words, pixels imaged at the different times are included in the image data of one frame.
In such a case, there is a concern that the control section 140 considers by mistake the position of the template that is different from the position of the template to be matched in the image captured at the present time as the position in which the similarity is maximized when performing the process of template matching, and computes the transportation amount of the transport target medium based on the position of the mistaken template. Because of this, there is a concern that the computation accuracy of the transportation amount of the transport target medium is decreased. Meanwhile, such a problem is not limited to a printing apparatus, and also occurs in the transporting apparatus that transports the transport target medium.